1. Field of the Invention
The invention relates to a film advancing and rewinding mechanism for a camera, and more particularly to mechanical rewind apparatus that automatically rewinds a roll of film once it has reached the end of the roll.
2. Description of Prior Art
Film winding and rewinding operations are accomplished in a number of ways in prior art cameras. In manually operated winding systems the film is advanced frame by frame by the operator until the end of the film is reached. When the film will wind on no further, the operator must then rewind the film manually by rotating a handle that turns the spool axis inside the film cartridge.
In motor driven winding systems it is often the case that the film automatically rewinds after a number of exposures are taken. This number is preset when the film is inserted. This type of device although relatively simple is open to misuse. Firstly, the maximum number of exposures that can be taken on a film may be greater than the number of exposures stated on the packaging. By setting the number to be too small the photographer may waste exposures unnecessarily Secondly, the operator may incorrectly preset the number of exposures on the film. The use of this type of rewinding mechanism may also limit the length of film that could be used in the camera to those regularly available.
To provide a motorized mechanism that automatically rewinds a film when it reaches the end of the roll regardless of the number of exposures, prior art devices employ a number of contacts and electronic components to determine when the end of the film is reached and to trigger rewinding of the film.